Vehicle restraints are utilized to increase safety at a loading dock. The restraints secure a truck trailer to the loading dock structure or building when goods are transferred between the trailer and the building. The restraints typically engage a rear horizontal bar referred to as the rear impact guard (RIG) or ICC bar. The RIG or ICC bar is located at the rear end of the trailer below the trailer bed. When the trailer is backed up to an available loading dock stall, the RIG bar is positioned close to the face wall of the dock. Bumpers typically extend from the face wall to protect the trailer, dock and any dock leveling fixture at the dock. Trailer restraints typically include a hooking device located in front of the dock and anchored to the dock or ground. When in use, the hooking device forms a barrier in front of the RIG bar to secure the trailer so that it cannot move away from the dock. The restraint helps avoid accidents by securing the trailer to the loading dock so that the truck driver does not inadvertently pull the trailer away when the trailer is being loaded or unloaded. The restraint also helps prevent the trailer from being pushed away from the dock during the process of loading and unloading the trailer. For example, a fork lift, particularly one carrying heavy cargo that rides onto the trailer and abruptly stops, tends to move the trailer away from the dock.
Conventional trailer restraints include storable restraints and impact restraints. Storable restraints move between a raised operating position and a lower stored position. When in the stored position, a trailer should clear the device as it is being backed into an available loading dock stall. Conventional storable restraints are disclosed in U.S. Pat. Nos. 4,488,325, 5,096,359, 4,964,777 and 7,384,229. When the trailer and dock leveler are properly positioned with the lip of the leveler resting on the trailer bed, the stored restraint is activated to rise up and securely engage the RIG bar. Restraint mechanisms of this style are powered into their raised position by motors, springs or other mechanical means. Impact restraints include a movable carriage that adjusts to the height of the trailer RIG bar. The incoming RIG engages a sloped portion of a carriage, which pushes the carriage down and into aligned engagement with the RIG as disclosed in U.S. Pat. Nos. 4,264,259, 4,560,315, 6,162,005 and 8,596,949 the contents of which are incorporated herein. The carriage has a drive system with a motor that rotates a hook from a release position to a securing or locking position as shown in FIG. 1A. An operator actuates the motor when the RIG engages and aligns over the carriage. The motor rotates the hook so that it emerges from the carriage and securely engages the RIG bar.
A problem with impact trailer restraints is that the hook can be forced down and out of engagement with the RIG bar by certain movements of the trailer during the process of loading and unloading the trailer. The restraints or their hook drive systems do not adequately accommodate the up and down, back and forth (i.e., trailer rocks toward and away from dock “dock-walk” and vibrational movements of the RIG during the loading and unloading process, such as when forklifts move heavy cargo on and off the trailer. This can result in the hook inadvertently “walking-off” or disengaging the RIG bar, and the RIG bar from “walking-off” or disengaging from the restraint during use. While a limited amount of “dock-walk” is typically not problematic, it is when the amount is sufficient to cause the hook to disengage the RIG bar, and putting the safety of the workers at risk.
Another problem with impact trailer restraints is that trailer RIG bar is frequently obstructed so that the hook cannot grip the upper corner of the RIG bar. As shown in FIG. 1B, an obstruction such as a plate spanning the length of the RIG bar prevents the top or grip disc of the hook from wrapping around the upper forward corner of the RIG bar. Instead, the top of the hook engages the forward surface of the obstruction, which is often a smooth or otherwise generally flat surface. This accentuates the problems posed by an inadvertent pull-away by the truck driver or “dock-walk” because there is no upper corner for the hook to grip and the hook can only engage the generally flat, smooth surface of the obstruction or the flat, smooth front surface of the RIG bar as in FIG. 1C. Thus, the hook can rotate down so that its tip move down and out of engagement with the RIG bar as shown in FIG. 1D.
A further problem with trailer restraints is the large loads they are designed to withstand. Trailer restraints are often rated to withstand 100,000 pounds of trailer pull away force. Restraints with load bearing components that are not robustly and reliably designed to withstand these forces will be damaged and require replacement or expensive servicing.
A still further problem with trailer restraints is the variety of trailer heights and RIG locations. RIG bars vary vertically from the ground and horizontally from the rear end of the trailer. The height of the rear end of the trailer and RIG bar from the ground can vary widely at a loading dock, particularly when the entrance to the loading bay is sloped and the rear end of the trailer extends significantly from rear axle of the trailer. The larger the carriage and restraint components, the more limited the restraint is in accommodating a variety heights of the trailer rear end and RIG bar. Yet, the usefulness of a restraint is reduced if it does not accommodate a wide variety of trailer and RIG designs.
A still further problem with trailer restraints is the limited space the restraint can occupy during operation and when being stored during periods of non-use. For loading bays equipped with a mechanical or hydraulic dock leveler, the restraint should be located below the pit floor so that it does not obstruct the operation of a dock leveler in the pit.
A still further problem with trailer restraints is that they are susceptible to wear and tear that can increase maintenance costs and produce unsafe conditions during use. Restraints are subject to harsh working environments. They are mounted outside where dirt, debris, snow, ice, rain, humidity and temperature all contribute to the wear and tear on the device. Elaborate and intricate mechanisms are prone to wear and binding. They require frequent servicing to ensure they function properly. For example, restraints can be damaged when the RIG bar impacts a bound or frozen carriage and attempts to force it down. When these mechanisms are not properly services, the hook is not held in place and they are susceptible to allowing the hook to inadvertently drop down and out of engagement with the RIG during use, and putting the safety of the workers at risk.
The present invention is intended to solve these and other problems.